MAT106: Wall Framing. AMERICAN FOREST & PAPER ASSOCIATION American Wood Council Engineered and Traditional Wood Products

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Norman Fowler
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1 MAT106: This portion of the program will address the code requirements for wall framing, although we won t address bracing in this section. The program contains a separate bracing section. 1

2 FASTEN PLATES BOLTS REQ D Code specifies Diameter Penetration Spacing Distance from end Let s start at the bottom. The default code requirements are that bottom plates be attached to the foundation with bolts. The code addresses minimum bolt diameter, minimum penetration into the foundation, maximum spacing between bolts, and the maximum distance from the end of each piece of plate for the first bolt. 2

Other devices must be approved In practice, however, we often see other devices. All of those devices are proprietary and there aren t any general statements to make about them except: 1.

3 Other devices must be approved In practice, however, we often see other devices. All of those devices are proprietary and there aren t any general statements to make about them except: 1. They aren t specifically recognized by the code and must be accepted under the alternate methods and materials section of the code. 2. In order to insure that these devices provide connection strength comparable to bolts, they must be used in accordance with the manufacturers recommendations. Typically users in the field want to space these devices farther apart than what s required by the manufacturers because they assume that they can be used in the same manner as bolts. 3

4 WALL HEIGHTS Stud lengths Bearing walls 2000 IRC vague 2003 edition 10 Table R for > 10 Nonbearing walls 2000 IRC not addressed 2003 edition up to 20 (2x6 for that height) The IRC addresses minimum stud lengths, although the 2000 edition is somewhat confusing. Because Table R addresses stud heights above 10 ft, the implication is that the default maximum stud height is 10 ft. However, the 2000 edition isn t specific. The 03 edition has been revised to clarify that the maximum stud height is 10 ft unless the provisions of Table R are followed. In the 00 edition of the IRC there s nothing to address nonbearing stud heights. The 03 edition limits nonbearing studs to 20 ft, although there are some other requirements placed on studs that are that high. 4

5 STUD SPACING IRC TABLE R602.3(5) STUD SPACING ROOF/CEILING FLR/ ROOF/CEILING 2 FLR/ ROOF/CEILING 2X4 24 (10 ) 16 (10 ) - 2X6 24 (10 ) 24 (10 ) 16 (10 ) If greater than 10 ft. see Table R602.3(1) Stud spacing is also limited, as we see here in a version of IRC Table R602.3(5). Spacing is limited by loading. 5

6 UTILITY GRADE STUDS IRC Section R602.2 Bearing walls can support no more than roof & ceiling (spacing 16 o.c.) No grade-specific limitations bearing wall height req ts same as other grades No limitations on use in nonbearing walls Utility Grade studs are relatively low-strength members and often look pretty rough. However, the code permits their use under the limitations that you see here. 6

7 GENERAL WALL FRAMING 3 studs at each corner Double top plate on exterior & bearing walls Overlap corners and intersections Offset end joints Joist/rafter bearing near stud Single top plate on interior nonbearing walls Overlap corners and intersections The general framing provisions for walls are similar to what s been in the UBC and SBC for a long time. We ll talk more in a moment about the details. 7

8 TOP PLATE DETAILS Joist Plate overlap IBC min. 48 IRC min. 24 Joist spacing Max. 5 Double top plate Wall studs Studs 24 o.c. Here are the requirements for top plates. Notice that the joints in the individual pieces of the top plates must be spaced no closer than is shown. The differences in the spacing requirements contained in the IRC and IBC shouldn t be a concern. This same difference existed between the Uniform Building Code and Standard Building Code, and there was no evidence of either of these numbers being more correct structurally than the other. Also notice that where roof/ceiling framing bears on the plate, it must be more-or-less above the studs if they are spaced at 24 o.c.. 8

9 CRIPPLE WALLS Stud size not less than wall above If more than 4 high, stud size as req d for an additional story If less than 14 high Solid blocking Sheathed one side with WSP If more than 14 bracing req d Cripple walls are addressed in some detail in the IRC, maybe more so than they were in the older codes. Because cripple walls often act like another story, details of their construction are important, particularly in high-seismic areas. 9

10 HEADERS The IRC contains pre-calculated headers tables. Users of the UBC will remember that it was pretty vague about headers. The SBC contained header tables, but they were different than what s contained in the IRC. 10

11 HEADER TABLES Tabulated header spans 4 main species Based on Ground snow load Building width Jack studs addressed 2000 edition: error in 4-2x8s (corrected in 2003 edition) Wood structural box header Header not req d in nonbearing walls There are pre-calculated header tables in the IRC. These also appear in the IBC. 11

12 NOTCHING & BORING OF STUDS Cutting of studs is probably one of the most common code violations. 12

13 Size & location of notches & holes limited Bored holes not allowed in same section as notch We ll see some examples of both code requirements and common violations in a moment. Although the code says that holes aren t allowed in the same section as notches, it doesn t explain what s meant by same section. Keep in mind that the intent is to preserve as much continuous wood fiber as possible to transfer forces, while still permitting some limited cutting of the fiber. Holes and notches placed so close to each other that they effectively destroy most of the fiber would be in violation of this requirement. 13

14 EXTERIOR & BEARING WALLS NONBEARING WALLS 5/8 min. from stud face Hole diameter max. 40% of stud width (60% if stud doubled max. 2 studs) Notch max. 25% of stud width Hole diameter max. 60% of stud width Notch max. 40% of stud width Here are illustrations of what the code permits. 14

15 Tie req d if > 50% TOP PLATES EXTERIOR WALLS & INTERIOR BEARING WALLS 16 gage (0.054 ) x 1-1/2 metal tie 6-16d nails each side of notch (2000) 8 16d nails each side of notch (2003) Stud Pipe Fig. R shows strap on one plate; text in 03 IRC R Indicates strap on both plates. ICC interpretation is to put strap on just one plate. 06 clarifies one strap. Double top plate One of the functions of the top plate is transfer lateral forces in the wall and help prevent racking (more on this in the bracing section). For that reason it s important that continuity of the plate be maintained if it s necessary to cut it. The code requirement is for 1. The metal splice plate to be of a minimum thickness and width, and 2. The nails on either side of the cut (6 req d in the 2000 edition & 8 req d in the 2003 edition) What it doesn t say is how those go together. This illustration is similar to what s in the code. Putting so many nails so close together may split the wood. It might be better if the strap were wide enough to span the cut in both levels of the top plate and the nails distributed in a wider fashion. Or if the steel plate were longer and the nails a greater distance from each other. Wood structural panels nailed across the cut would accomplish the same thing. Also not addressed is whether the top plate can be completely cut and how to compensate for that situation. 15

16 Here s an example of notching and boring of studs in compliance with the code. A point to make here is that the straps that you see on the face of the studs don t do anything to compensate for over-cutting. They simply provide protection of the pipes from nail puncture. There are, however, proprietary products that are intended to reinforce the stud if it s over-cut. 16

17 Here s an example of a violation the holes are too near the face of the stud. 17

18 At first glance, this appears to be in compliance with the code. However, it might be that these two pipes have effectively destroyed the continuity of the wood fiber in the stud by cutting out most of the wood fiber in one section of the stud. And it looks as if the black pipe may be too near the back face of the stud. Again, the strap doesn t compensate for those problems. 18

19 Since most violations occur as a result of trying to put pipes into a wall, here s a good solution: a double-stud wall. 19

20 > 40/60% Width Here s another solution when accommodating large pipes using wider studs. However, in this example because of the angle of the pipe the hole is larger than allowed, and it may be too close to the face of the stud. 20

21 And when wider studs are used it s important that they rest completely on a plate. The code requires for the plate to be at least as wide as the studs. 21

22 WALL BRACING - Next Segment And important consideration in the IRC s wall requirements is bracing. We have a complete section on that subject. 22

23 QUESTIONS? 23

2x6. 2x8. 2x10. Size. 2-2x10 8'-5" w/ 2 NJ 7'-3" w/ 2 NJ

2x6. 2x8. 2x10. Size. 2-2x10 8'-5 w/ 2 NJ 7'-3 w/ 2 NJ 1 Rafter Size Spacing Allowable span 24" 11'-9" 24" 2x6 14'-1" 2x4 12" 15'-6" 12" 24" 14'-10" 24" 2x8 18'-2" 2x6 12" 20'-5" 12" 24" 18'-2" 24" 2x10 22'-3" 2x8 12" 25'-8" 12" 24" 21'-0" 24" 2x12 25'-9"